Method and device for casting voids



Jan. 15, 1963 J. c. BUXTON METHOD AND DEVICE FOR CASTING voms Filed July 5, 196

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United States Patent Otiice 3,072,995 Patented Jan. 15, 1963 3,072,995 7 METHOD AND DEVICE FOR CASTING VOIDS Jarvis C. Bnxton, Portland, reg., assignor to Griflith Rubber Mills, Portland, 0reg., a corporation of Oregon Filed July 5, 1960, Ser. No. 40,898

12 Claims. (Cl. 25128) This invention relates to the casting of voids, and more particularly'to a method and means for casting voids in concrete members.

In the manufacture of concrete members, such as certain kinds of structural beams and the like, it is customary to form the members with voids extending through the interiors of the members. Such voids not only lessen the weight and cost of a beam, but provide a passage through the beam, useful, for instance, when prestressing the beam or when it is desired to pass a conduit through the beam.

Heretofore, in order to provide such voids, various methods and devices have been employed. According to one form of practice, an inflated rubber sleeve ismounted within a mold and this functions as a core element when concrete is poured into the mold and about the sleeve. Afterthe concrete sets, the sleeve is deflated and removed from the hardened concrete. A principal shortcoming of this method is the difficulty in fixing the position of the sleeve in the mold. As concrete is poured around the sleeve, the sleeve ends tend to shift in position, and the sleeve also may. bend or bow between its ends, result ing in the formation of an imperfect void. Further, there has existed lackof control over the shape of the sleeve after inflation.

According to other methods, various types of solid members are used as core elements, around which concrete is poured. The use of such members, however, poses problem in erection and removal. They also often are expensive, as well as cumbersome and hard to manipulate.

This invention contemplates an inflatable core element, and means for partially shaping it and mounting it in fixed position in a form, comprising elongated tension members fastened to the core element that in inoperative position are flexible, but that can be tensed by pulling apart their ends so as to stiffen the tension members. The core element is readily mounted usingthe tension members so that it will not move when concrete is poured around and over it, yet the core element can easily be removed from the, form after the concrete has set. ;Bend ing or bowing of the core element is inhibited, and the shape of the element can be controlled in a manner that is impossible with prior-known, inflatabledevices.

In an embodiment of the invention, an inflatable elongated hollow core element has at least two longitudinally extending cables fastened to the longitudinal wall of the 7 core element, with ends of the cablesprojecting out from the core element deflated, which has the effect of loosen ing the'element so that it can be pulled" axially outof the hardenedconcrete.

Thus an object and feature of the invention -is--to'provide a core element withcables along its length that can be tensioned,whereby once the core element is placed in a form and its cables put under tension, thecore element becomes self-supporting, and the position of'the core element inthe form is fixed- Thus the. coreelement material.

is prevented from shifting as concrete is poured under, around, and over thecore element.

Another feature of the invention is the provision of a core element with unique means for stiffening it along its length, comprising flexible tension members fastened to the core element and extending along the length thereof adapted to be tensioned by pullingapart the ends of the members. The core element is readily made flexible and yieldableby relaxing the tension in the tension members.

Voids cast inconcrete using the core element of the invention are correctly positioned, unobstructed, and clean-walled.

These and other objects, features and advantages are discussed in the following description, taken in conjunction with the accompanying drawings, in which:

HG. l is'a top plan view of a core element according to the invention, showing it positioned in a concrete forni;

FIG; 2 is a cross-sectional view, taken along the line 2-2 in FIG. 1;

FIG. 3 is a cross-sectional view, showing an alternative configuration for a core element according to the invention;

FIG. 4 is a cross-sectional view showing another alternative configuration for a core element according to the invention; and

FIG. 5 is a top plan view showing parts of a core elementas contemplated by the invention, and a modified form of mounting for the core element in a form.

Referring to the drawings, and particularly to FIGS. 1 and 2, 10 generally indicates an elongated core element or fluid container made according to the invention. The core element shown has a hollow body or member defined by longitudinal or side walls 1 1, and end walls 12 closing off the ends of the body. The body in the embodiment of FIGS. 1 and 2 has a rectangular cross section, and the walls defining the body preferably are made of flexible and resilient material, such as rubber or a synthetic. Fastened to longitudinal walls 11, as by embedding them in the walls, are plural, flexible, tension cables or means 13. These ordinarily are made of steel or other suitable Cables 13 extend longitudinally of the core element, -and run continuously through walls 11. The cables have end portions 14 that project out of and thus extend free from the core element Extending through an accommodating opening providedin one end wall 12 of the core element and fastened in the end wall is a conduit secti-on16. The'interior of the conduit section connects with the interior of the core element. The conduit section is connected to a valve 27 used tocontrol the flow of fluid to and from the interior of the core element. Valve '17 may be adjusted to one'pos'ition to enable pressure fluidto flow intothe core element from a-source 18. In anotherpo'sition the flow of fluid from the source is cutoff, and fluidmay be exhausted from the core element through discharge conduit 19. In still another position for the valve, conduit section 16 is closed off to hold fluid within'the core element. 7 The mechanism described constitutes inflation-deflation means for'the core element. V Moun-ted ineach end wall 12 of the core element isa cable spacerand reenforcingplate 15. These add strength to the ends of core element 10, and hold the cables pro-pa erly distributed in longitudinal walls 11 between the end walls, against any tendency that tensioning. of the cables, by pulling aparttheir ends, may have to shift their position. V y I The core element is mounted in a concrete form 2%,

shaped as a rectangular box with an open top. Form 20 has openings 21 at its ends, that accommodate ends of the core element projecting out of the form. While only scrapes 3 be understood that larger concrete forms could be used, in which a plurality of core elements are so positioned.

The core element may take any of a variety of different configurationsv As shown in FIG. 3, a core element w has a hollow body with a circular cross section, and two tensioning cables 13a are positioned along diametrically opposite sides of the element. The core element includes circular reenforcing plates 15a. ment 10b with a hollow body having a triangular cross section is shown, in which there are plural cables 13!) spaced in the longitudinal walls of the element and supported at the ends of the element in triangular-shaped reenforcing plates 15b. Each has conduit sections (16a and 16b, respectively) opening to the interior of the core element for inflating and deflating the element. I I

With the core element positioned in form 20, the ends 14 of each cable 13 are pulled apart so as to tension the cable, and the ends are then anchored in place. Thus, with reference to FIG. 1, fixed retainer walls adjacent each end of the core element and outside form 20 are indicated at 23. The cables of the core element extend through suitable apertures provided in the retainer walls, and are held in place, using cable clamps 24. The cables are tensioned prior to final positioning of clamps 24, by any suitable means, as by a hydraulic jack or similar tension-producing mechanism.

The cables, as in all of the embodiments described, preferably are evenly distributed about the cross section of a core element, so that when they are tensioned, all sides of the core element are approximately equally supported by the cables.

In FIG. 5, a modified construction for the form and core element is shown. Here the end of a core element 100 is shown mounted completely within a form 200, and cables 130 at the end of "the core element proceed from the core element and thence through the end wall of the form, where they are anchored in place by clamps 24c bearing on retainer wall 230. In this embodiment, as well as in the other embodiments discussed, the position of the core element is determined by the position of the cables, and tensioning of the cables partially shapes and stitfens the core element.

In the embodiment of FIG. 5, a snug fit is provided around the cable ends where they pass through an end wall of the form, prior to pouring concrete, to prevent leakage. In the embodiment of FIG. 1, it is the body of the core element that is snugly fitted in the end walls of a form.

Describing the manner in which the core element of the invention may be used, the core element, in a deflated condition, is placed in a form, and its conduit section 16 suitably connected to a valve and source, such as that shown at 17 and 18. Cables 13 are then tensioned until the position of the core element is firmly fixed, and clamps 24 are then applied to anchor the cable ends. Tensioning of the cables partially shapes the core element and stiifens it. Thereafter, via valve 17, the core element may be inflated to the desired degree. Concrete is then poured all around and over the core. After the concrete has set, the cable ends are released, and valve 17 opened, to permit deflation of the core element and relaxing of the tension in the cables. This makes the core element entirely flexible. The valve is then disconnected from the end of the core element, and the element may be pulled axially out of the hardened concrete by any suitable pulling means, to leave the desired void in the concrete. The core element may, of course, be used over and over for casting other voids.

In many instances the preferred pressure fluid used for inflating the core element comprises a liquid, such as water and the like. The core element when inflated may be quite heavy, and exert unduly large forces on the structure mounting it in the absence of any concrete under the element. In such circumstances it is sometimes preferable to defer inflating the core element until enough con- In FIG. 4, a core elecrete has been poured to provide some support for the base or bottom side or the element.

The core element of the invention exhibits little tendency to bow or bend between its ends. The ends of the element stay anchored in place during pouring and will not pull out of position.

Although the invention has been described in connection with the use of concrete, it should be understood that the core element of the invention lends itself to use with any other ce'rnentitious or plastic-type material which sets or solidifies. I I

While the invention has been described in connection with preferred embodiments, it will be obvious to those skilled in the art that modifications and changes may be made, and it is intended to cover all such modifications and changes and to limit the invention only as defined in the appended claims.

It is claimed and desired to secure by Letters Patent:

1. A device of the character described for providing voids in poured cementitious members comprising a hollow fluid-tight container having flexible surrounding walls defining the sides thereof, at least two elongated tension members fastened to opposite sides of the container and each with opposite ends extending free from opposite ends of the container, means connecting with the inside of the container for controlling inflation and deflation of the container, and means connected to said opposite ends of said tension members for tensioning them externally of the container. I

2. Mechanism for use in conjunction with a concrete form to provide a void in concrete poured in the form comprising an elongated hollow flexible member with elongated side Walls and opposed end walls defining a hollow fluid-tight interior for the member, a plurality of longitudinally extending cables embedded in the side walls of the flexible member, each of said cables extending at opposite ends out beyond the end walls of the flexible member, means including a valve connecting with the interior of the flexible member for permitting inflation and deflation of the flexible member, and means connected to said opposite ends of said cables for tensioning them externally of the flexible member.

3. The mechanism according to claim 2 and in which the cables are equally spaced from each other in the side walls of the flexible member.

4. The mechanism according to claim 2, which further comprises a cable-spacing plate adjacent each end wall of the flexible member engaging the cables.

5. The mechanism according to claim 2 and in which 7 the hollow flexible member has a triangular cross section and at least a portion of said cables are at the corners of said cross section.

6. The mechanism according to claim 2 in which the hollow flexible member has a rectangular cross section and at least a portion of said cables are at the corners of said cross section.

7. The method of casting voids in concrete members using an elongated, flexible, inflatable core element and a surrounding concrete form which comprises arranging the core element in the concrete form and placing the element in fixed position while pulling externally on the ends thereof to place the same under longitudinal tension, inflating the element, pouring concrete in the form to cover the element, permitting the concrete to set, and removing the longitudinal tension from the element and deflating the element, so as to enable its removal from the poured concrete.

8. The method of claim 7 wherein the core element is placed in a position above the bottom of the form and concrete to support the bottom of the core element is poured into the form prior to inflating the core element.

9. In an elongated flexible core element having means whereby the same is inflatable with fluid so as to be shaped by the fluid and used to form the interior of hollow concrete members, the improvement comprising tension means for shaping the core element, said tension means comprising plural elongated tension members that in inoperative condition are flexible, said tension members being fastened to the sides and extending along the length of the core element with ends free of the ends of the core element, and means for anchoring the ends of the tension members while they are under tension thus to stiflen the core element.

10. Mechanism for making voids in poured cementitious members comprising an elongated and flexible fluid-tight container having side and opposed end walls, plural longitudinally extending cables embedded in and secured to the side walls of the container, each of said cables extending at opposite ends beyond the end Walls of the container, means for inflating and deflating said container, means anchoring each cable in the container adjacent each end Wall of the container, and means connected to the opposite ends of each cable Where it extends beyond said end Walls for tensioning the cable externally of the container.

11. Mechanism for making voids in poured cementitious members comprising a hollow form, an elongated flexible fluid-tight container mounted Within said form, a plurality of longitudinally extending cables embedded in and secured to the side Walls of said container, each of said cables protruding at opposite ends out beyond the ends of the container, means holding the protruding ends of said cables with the cables tensioned and the side Walls of said container that are joined to the cables also tensioned, and means connecting with the interior of said container to enable the inflation thereof.

6 12. The method of casting voids in concrete members using an elongated flexible inflatable core element and a surrounding concrete form which comprises arranging the core element in the form, pulling on the ends of the core element at locations at each end equally distributed around the core element to place the element in longitudinal tension and then fixing the ends of the core element in place, with the core element in longitudinal tension inflating the core element, pouring concrete in the form to cover the core element, and after the poured concrete has set removing the longitudinal tension from the core element and deflating the element so as to enable removal of the element from the concrete.

References Cited in the file of this patent UNITED STATES PATENTS 1,456,058 Hale May 22, 1923 2,170,188 Cobi Aug. 22, 1939 2,192,183 Deutsch Mar. 5, 1940 2,312,587 Price Mar. 2, 1943 2,612,673 Billner Oct. 7, 1952 2,628,402 Billner Feb. 17, 1953 2,765,511 Greene Oct. 9, 1956 2,892,239 Nefi June 30, 1959 2,892,339 Flower June 30, 1959 2,977,658 Smith et a1 Apr. 4, 1961 FOREIGN PATENTS 784,184 Great Britain Oct. 2, 1957 

1. A DEVICE OF THE CHARACTER DESCRIBED FOR PROVIDING VOIDS IN POURED CEMENTITIOUS MEMBERS COMPRISING A HOLLOW FLUID-TIGHT CONTAINER HAVING FLEXIBLE SURROUNDING WALLS DEFINING THE SIDES THEREOF, AT LEAST TWO ELONGATED TENSION MEMBERS FASTENED TO OPPOSITE SIDES OF THE CONTAINER AND EACH WITH OPPOSITE ENDS EXTENDING FREE FROM OPPOSITE ENDS OF THE CONTAINER, MEANS CONNECTING WITH THE INSIDE OF THE CONTAINER FOR CONTROLLING INFLATION AND DEFLATION OF THE CONTAINER, AND MEANS CONNECTED TO SAID OPPOSITE ENDS OF SAID TENSION MEMBERS FOR TENSIONING THEM EXTERNALLY OF THE CONTAINER. 